1. Field of the Invention
The present invention relates to a system for transporting workpieces and associated load carriers in manufacturing operations, and more particularly to a method and apparatus including main and auxiliary paths for the load carriers, and computer-controlled identifying, holding, and diverting devices for transferring load carriers from the main path to the auxiliary path and then to a work station, while optimizing the workpiece passage times around the system.
2. Description of the Related Art
An automatic workpiece transport and routing device is known (Federal Republic of Germany OS No. 17 81 310), which includes a power drag means and a conveyor, the load carriers which can travel on an endless main path being moved by the drivers provided at given distances apart on a continuously driven conveyor. Each load carrier has a respective coded address part which is scanned by scanning apparatus arranged alongside the main path. Beside the main path there are provided auxiliary paths over which the load carriers can travel via switchable switches. There are also buffer paths into which the load carriers are switched depending on their address code and, after the completion of the working of the workpiece carried by the load carrier, brought back into the main path. The known transport device has the following disadvantages:
1. Since one driver of the conveyor belt always moves only one load carrier, and as a result of the distance between each two drivers, intolerably long passage times result.
2. Since directly before the working of the workpiece transported by the load carrier said load carrier can neither be placed on or transferred from the auxiliary path, a simultaneous sorting operation is not possible during the working of the workpiece.
3. For the presorting of similar workpieces, a plurality of buffer paths will branch off from the main path and are arranged parallel to each other are provided in front of the work station, as a result of which the known device takes up a very large amount of space.
A principal object of the present invention is to provide a method by which shorter passage times during the course of manufacture can be obtained while, at the same time, the sorting of workpieces which have still not been worked can be carried out during the working of a given workpiece. A further object is to provide an apparatus for carrying out the method which takes up a minimum amount of space.
This object is achieved in a computer-controlled system in which each workpiece is placed on a load carrier, each workpiece and load carrier being marked with an identifier. A central computer is loaded with data relative to each given workpiece, its respective load carrier, and work to be performed on such workpiece, and predetermines a path to be followed by such load carrier. The load carrier is placed on a main path, its identifier is read, and if work is to be performed on a workpiece carrier thereon, a switch is thrown to divert the load carrier to an auxiliary path and then to a work station. The load carrier may be diverted to the work station by a swing-out device or by a spur path, for example. After such work, the load carrier is returned to the main path and its identifier is read again to determine whether it again is to be diverted to an auxiliary path for performing further work on a workpiece carried thereon. Holding devices are provided on the main and auxiliary paths for performing sorting and accumulating functions to optimize passage times around the system.
By the computer-assisted method of the invention it is now possible, for the desired shortening of the passage times, to assure an optimized flow of material to the individual work stations which substantially eliminates non-productive downtimes, the pieces of material to be worked being presented to the operator in optimal ergonomically favorable position for grasping, relative to the work center of each working station. For this purpose, the apparatus for the carrying out of the method permits automatic sorting, adapted to specific requirements, in the immediate vicinity of the corresponding work station, as well as the delay-free removal from said work station of the workpiece which has been worked. The computer-assisted method furthermore also permits the preferred working of rush orders and other special jobs by priority criteria stored in the central management computer, considerable efficiency being obtained by this method, particularly in the garment industry.